Optimized DNA and protein sequence of an antibody to improve quality and yield of bacterially expressed antibody fusion proteins

Abstract

Object matter of the invention is an optimized DNA sequence encoding the scFv(FRP5) antibody fragment. This novel sequence prevents the generation of the undesired by-product in the context of an scFv(FRP5)-ETA fusion protein, and possibly also other bacterially expressed scFv(FRP5)-containing fusion proteins. The DNA sequence of the scFv(FRP5) domain of scFv(FRP5)-ETA was modified by exchanging a distinct codon, thereby preventing an otherwise possible internal start of protein translation.

Description

[0001]This application claims the benefit of U.S. Provisional Application Ser. No. 60 / 949,580 filed Jul. 13, 2007, the contents of which are incorporated by reference herein in their entirety.[0002]The antibody-toxin scFv(FRP5)-ETA is a recombinant fusion protein composed of a single-chain antibody fragment derived from the ErbB2-specific antibody FRP5, via gene fusion linked to a truncated fragment of Pseudomonas exotoxin A. High and selective antitumoral activity of scFv(FRP5)-ETA against ErbB2 expressing cancer cells in vitro, in animal models and in cancer patients has been described in detail in the literature. Production of scFv(FRP5)-ETA by bacterial expression in E. coli using current methodology results, in addition to the major product of intact scFv(FRP5)-ETA, also in a truncated scFv(FRP5)-ETA fragment as a by-product. Complete elimination of this undesired fragment using classical protein purification techniques has so far not been achieved.[0003]Object matter of the in...

AI Technical Summary

Benefits of technology

[0008]It is an object of the invention to prevent the generation of this truncated fragment of scFv(FRP5)-ETA without affecting the therapeutically relevant biological activities of the full-length protein. Upon application of this invention, this undesired by-product can no longer form during bacterial expression. Therefore protein preparations of higher purity can now easily be produced.

[0018]The single-chain recombinant antibody may further comprise an effector molecule and / or signal sequences facilitating the processing of the antibody by the host cell in which it is prepared.

[0036]The polypeptide of the invention optionally comprises another peptide, e.g. a peptide facilitating purification, in particular a peptide being an epitope against which an antibody is available, such as the FLAG peptide. Purification, e.g. by means of affinity chromatography, of a fusion protein comprising such a peptide is advantageous e.g. in that it may be faster, more specific and / or gentler. The peptide may be placed at the N-terminus of the fusion protein, in between the recombinant antibody and the effector molecule, or at the C-terminus of the fusion protein. Preferably, it is located at the N-terminus or at the C-terminus, in particular at the N-terminus. Preferably, these constructs also contain a cleavage site, so that the fusion protein can be liberated therefrom, either by enzymatic cleavage, e.g. by enterokinase or by Factor Xa, or by the chemical methods known in the art. Furthermore these constructs may comprise a peptide spacer consisting of one or more, e.g. 1 to 10, in particular about 2 amino acids, said spacer facilitating the linkage of the above-mentioned peptide and / or the cleavage site to the recombinant antibody. The cleavage site is placed in such a way that the fusion protein comprising the recombinant antibody and the effector molecule can be easily liberated, if desired, preferably in vitro. For example, in a protein construct comprising the fusion protein designated scFv(FRP5)-ETA, the FLAG peptide and an enterokinase cleavage site are linked to a spacer and placed in front of the Fv heavy chain / light chain variable domain and exotoxin A fusion protein. If desired, the FLAG peptide can be cleaved off by enterokinase, preferably after affinity purification of the protein, yielding a fusion protein comprising the single-chain antibody Fv(FRP5) and exotoxin A.

Problems solved by technology

By-products contaminating preparations of the active compound may cause adverse events in a patient, such as toxic reactions, and / or the induction of undesired immune responses.

As a consequence, production costs will dramatically increase due to the requirement for sophisticated and expensive purification techniques used to remove such undesired by-products, and / or due to additional testing that is required if a particular by-product cannot be removed.

Using standard protein purification techniques, it has not been possible so far to remove this truncated protein fragment.

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